1. Field of the Invention
The present invention refers to the field of construction of road substructures, referring in particular to the construction of embankments for road and/or railway structures.
Embankments are defined as those works whose funtion is to support the roadway at higher levels with respect to the levels of the surrounding land. Such function is required when levels must be reached which are necessary for crossing any obstacle to the route (water courses, roads, railways etc.) by means of a bridge, or when the natural morphology of the land does not allow the construction of roads, in narrow zones, with the necessary altimetric characteristics (limited variations in gradient),
2. Description of the Background Art
The state of the art comprises the use of natural soil with special characteristics for the realization of embankments, The materials employed in the realization of the embankments are, in the first place, dry earth, gravel and sand. It is also possible to use mixed-type earth (sand silt or sandy clay), paying particular attention to laying the mixed-type earth in its original place. Unfortunately the best materials for building embankments are difficult to find in the trade because of the limited availability of quarries for their extraction, being subject to increasingly tight restrictions. Therefore the choice often falls on the use of materials which are easier to find but scarcely suitable for the required use, and which, therefore, require additional processing and particular attention for being correctly laid in-situ.
The characteristic cross sectional shape of embankments is a trapezium, with its smaller base consisting of the roadway and the sides sloping obliquely. It is easy to deduce that the planimetric overall dimensions of an embankment of average height (5-6 metres) are considerable; for example, for a height of 5 metres and an inclination of 2/3, 15 metres of ground beyond the width of the roadway are needed just for the slopes.
A further drawback with traditional embankments consists in the weight of the embankment itself, which involves the risk of the embankment warping or sagging with respect to the plane of site, or of differential sagging along the development of the embankment itself; it should be noted that the embankment/foundation contact pressures are about 90,0/95,0 kPa, equal to those which a 10-storey building might exert on a continuous two-dimensional foundation.
Recently, in an attempt to avoid, in part at least, the above-mentioned drawbacks, extra-light standard size and shape cellular blocks made of thermoformed plastic material have been put on the market; such blocks have a shape with several honeycomb cells, and they are positioned side by side with each other on work and they are overlapped at random; then they are covered with a non-woven fabric and covered over with earth.
These elements, however, do not collaborate structurally with each other, and besides they do not avoid the necessity of realizing the embankments with lateral slopes, and hence with the overall dimensions and drawbacks involved.